In a chain transmission device including a driving sprocket attached to a crankshaft, driven sprockets attached to respective camshafts, and a timing chain (hereinafter, simply referred to as “chain”) made of metal, and trained around the driving sprocket and the driven sprockets, the chain transmission device being used for driving the camshafts, a pivotable chain guide is provided on one side of the loose side chain portion of the chain so as to extend along the direction in which the chain moves, and an adjustment force is applied to the pivotable end portion of the chain guide by a chain tensioner such that the chain becomes tensioned, thereby preventing the chain form becoming loose or flapping.
Also, a fixed chain guide is mounted to the tension side chain portion of the chain such that both end portions of the fixed chain guide are supported by respective supporting members. The fixed chain guide guides the movement of the chain, while preventing the chain from flapping.
As the chain guide for adjusting the tension of the chain or the chain guide for guiding the movement of the chain, a sliding-type chain guide is known which guides a chain by coming into sliding contact with the chain. However, in such a sliding-type chain guide, there is the problem that the resistance to the movement of the chain is large so that the transmission loss of torque is large.
In order to overcome such a problem, the applicant of the present application has proposed, in PCT International Publication No. 2010/090139, a chain guide including a guide base made of synthetic resin, and elongated in the direction in which a chain moves, a plurality of roller shafts arranged so as to draw a curved line, and each having both end portions supported by the guide base, and rollers comprising roller bearings, and being rotatably supported by the respective roller shafts, the rollers movably guiding the chain.
Since the rollers roll to guide the chain in the above chain guide, the resistance of the movement of the chain is small so that the transmission loss of torque is small.